From owner-freebsd-hackers  Mon Nov  2 20:47:06 1998
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To: "Larry S. Lile" <lile@stdio.com>
cc: hackers@FreeBSD.ORG
Subject: Re: "panic: free: multiple frees" VM bug? (long) 
In-reply-to: Your message of "Mon, 02 Nov 1998 23:38:48 EST."
             <Pine.BSF.3.96.981102233415.18310B-100000@heathers.stdio.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Mon, 02 Nov 1998 20:48:22 -0800
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>>    contigmalloc() isn't just a special version of malloc() that allocates
>> contiguous pages. It's actually a special allocator that has nothing to
>> do with malloc() and it is thus entirely incorrect to call free() with
>> a pointer to something that was allocated by contigmalloc(). The proper
>> way to free stuff that was allocated with contigmalloc() is with kmem_free().
>>    contigmalloc() is poorly named and should never have been brought into
>> the kernel that way.
>
>>From vm_extern.h
>void kmem_free __P((vm_map_t, vm_offset_t, vm_size_t));
>
>What would my parameters be? More specifically vm_map?  Just an
>example, I know I will have to write a oltr_free to do free/kmem_free
>based on how the memory was allocated.

   contigmalloc() allocates from the kernel_map, so that is what you need
to specify to kmem_free(). The offset is just the address that contigmalloc()
returned.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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